import java.util.*;
import java.math.*;

public class Solution {
  public static void main(String[] args) {
    BigInteger a;
    BigInteger two = BigInteger.valueOf(2);
    BigInteger zero = BigInteger.ZERO;
    BigInteger l, h, mid, tmp;
    Scanner cin = new Scanner(System.in);
    a = cin.nextBigInteger();
    l = BigInteger.valueOf(1);
    h = a;
    while ((h.subtract(l)).compareTo(zero) == 1) {
      mid = h.add(l);
      mid = mid.divide(two).add(BigInteger.ONE);
      tmp = mid.pow(2);
      if (a.compareTo(tmp) == -1) {
        h = mid.subtract(BigInteger.ONE);
      } else {
        l = mid;
      }
    }
    System.out.println(l);
  }
}
